1. Field of the Invention
This invention relates to the separation of ethylbenzene from complex admixtures of aromatic hydrocarbons including xylenes. The invention more directly relates to the recovery of ethylbenzene by selective adsorption using certain crystalline aluminosilicate zeolitic molecular sieves. The invention relates specifically to the operating temperature and desorbent composition which provide unexpected benefits.
2. Related Art
Those skilled in the art are familiar with a number of adsorptive separation methods which may be employed to perform the separation of aromatic hydrocarbons. The separation of C.sub.8 aromatics using zeolitic adsorbents has been described in the literature. For instance, U.S. Pat. No. 3,867,470 issued to P. F. A. Van Grinsven et al. is directed to the adsorptive separation of ethylbenzene from a mixture of C8 aromatic hydrocarbons using a Faujasite X which may be exchanged with cesium ions.
U.S. Pat. No. 3,943,182 issued to R. W. Neuzil and D. H. Rosback describes the use of zeolite X which has been ion exchanged with a Group I-A metal which may be cesium to recover ethylbenzene from admixture with xylenes. Accompanying this disclosure is a discussion of the use of para-diethylbenzene or mixtures of p-diethylbenzene and benzene as a desorbent, and the importance of such operational parameters as the silica to alumina ratio of the zeolite and the amount of water on the zeolite as measured by loss on ignition (LOI) techniques.
U.S. Pat. No. 4,593,149 issued to D. M. Barthomeuf also describes the recovery of ethylbenzene from ethylbenzenexylene mixtures through the use of a cesium exchanged X zeolite. This reference broadly describes suitable individual desorbents including diethylbenzene and toluene.